This invention relates to two-way radio communication systems in general and particularly to a system wherein the power efficiency of portable radio transceivers utilized in this system can be enhanced. In conventional two-way radio communication systems, such as an FM system utilized at VHF/UHF frequencies, a central system, which can be a trunked radio communication system, a repeater, or a base station which could serve as a telephone interconnect, uses a single modulation format for transmissions both to and from the portable or remote radios and the central system. In such systems, reasonable power efficiencies of the receivers of the portable transceivers can be achieved. Where a wide area of coverage is required, high transmit power levels are required in the portable radios. Such power levels can require a substantial percentage of the battery energy of the portable radios. It is to be desirable to provide a system in which the energy consumed in transmitting signals from the portable radios to the central system can be reduced. It is also desirable that the system be operable to the greatest extent with existing equipment.